Body Fat Percentage Calculator
The body fat calculator uses the US Navy method, which estimates your body fat percentage from tape-measure circumference readings and height, and shows your fitness category plus fat and lean mass.
verified_userReviewed by the Calculopedia editorial teamLast updated 2026-08-15
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quizExample
How this calculator works, with real numbers (no JavaScript needed):
Inputs
- Gender
- male
- Weight
- 75
- Height
- 175
- Neck circumference
- 38
- Waist circumference
- 85
- Hip circumference
- 95
Results
- Body fat percentage
- 10.6
- Category
- Athletes
- Fat mass
- 7.9
- Lean body mass
- 67.1
functionsThe formula
Your body fat percentage is a more honest health metric than weight alone, because it separates the fat you carry from the muscle, bone and water that make up the rest. Two people can weigh the same yet have completely different amounts of body fat — and it is the fat, not the weight, that most strongly predicts metabolic health.
Why it beats BMI for athletes
The classic example is a muscular athlete: BMI uses only height and weight, so it can label a heavily muscled person "overweight" even though their body fat is low, while missing the opposite problem in someone with a "normal" BMI but too little muscle and excess fat. Body fat percentage cuts to the point by measuring fat directly. Roughly speaking, essential fat is needed for basic function, and fat beyond healthy ranges tends to cluster around the organs where it is most metabolically active.
The US Navy method
It estimates body fat from circumference measurements — no calipers or scans needed. The formula (measurements in inches; the calculator converts your centimetres):
Men: 495 ÷ (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450
Women: 495 ÷ (1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.221·log₁₀(height)) − 450
This approach traces back to the U.S. Navy body-composition tables, which were developed to assess recruits rather than seeing them undergo caliper testing at scale. The Navy method is still popular today because it needs only a tape measure and gets surprisingly close to more expensive techniques — it assumes fat is distributed predictably with body size, which is generally true at the population level even if imperfect for any one person.
Measuring correctly
- Neck — just below the larynx, at its widest point.
- Waist — for men, at the navel; for women, at the narrowest point.
- Hip (women) — at the widest point of the hips.
The tape should sit snug but not dig in. Accuracy is about ±3 percentage points — good enough to track changes over time, not to obsess over one reading. Measuring technique matters more than any part of the formula: a tape that sits too high or too loose can shift the result by several points, so keep measurements consistent between sessions (same time, same spot) if you want to see real change.
Categories (ACSM)
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Acceptable | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Below essential-fat levels is unhealthy for everyone. Higher ranges raise the risk of metabolic disease — which is why body fat matters even when BMI looks "normal". These bands are population guidelines; the best way to use your number is to focus on its direction over time rather than a single label.
helpFrequently asked questions
question_markHow do I calculate my body fat percentage?
The US Navy method uses height plus waist and neck (and hip, for women) circumferences in a log formula. This calculator does the math instantly from your centimetre measurements.
question_markWhat is a healthy body fat percentage?
For men, 14–24% is generally healthy; for women, 21–31%. Athletes sit lower (6–13% men, 14–20% women), while 25%+ (men) and 32%+ (women) is considered obese.
question_markHow accurate is the Navy method?
Within about ±3 percentage points of lab methods like DEXA when measured correctly. It is best used to track trends over time rather than to judge a single reading.
question_markWhat is the difference between BMI and body fat percentage?
BMI uses only height and weight, so it can misclassify muscular people as overweight. Body fat percentage measures actual fat, giving a more accurate health picture.